old_string='hello woRld'
upper_str=old_string.upper()
lower_str=old_string.lower()
cap_str=old_string.capitalize()
title_str=old_string.title()
print(f'upper方法：{upper_str}')
print(f'lower方法：{lower_str}')
print(f'capitatlize方法：{cap_str}')
print(f'title方法：{title_str}')